Biology subjects

Lepcha, T. T.

Publications and source records attributed to Lepcha, T. T..

5 recordsLinked to original sources

bioRxiv2026

Levosimendan inhibits HIV-1 infection in myeloid cells in the RIOK1-dependent manner

Despite of the highly potent antiretroviral therapies, HIV-1 establishes persistent infection and causes chronic inflammation in AIDS patients. Beyond CD4+ T cells, HIV-1 infects myeloid cells, including circulating monocytes and tissue-resident macrophages, and integrates with host genomes to form stable viral reservoirs. To achieve a functional HIV cure, latency-promoting agents (LPAs) have been developed for the "block-and-lock" strategy to reinforce deep HIV-1 latency and permanently silence proviruses. However, most LPAs have been tested mainly in CD4+ T cells, and their efficacy in myeloid cells remains unclear. In this study, we reported that levosimendan (LSM), a drug approved for clinic use to treat heart failures, is able to inhibit HIV lytic infection and reactivation in myeloid cells. LSM blocked viral lytic reactivation in HIV-1 latently infected monocytic cells (TH89GFP, U1) and microglial cells (HC69). LSM also inhibited HIV infection in human induced pluripotent stem cell (iPSC) derived microglia (iMG), primary human resident liver macrophages (Kupffer cells) as well as human monocyte-derived macrophages (MDMs). Furthermore, we demonstrated that overexpression of a predicted drug target of LSM, the conserved serine/threonine kinase RIOK1 (RIO kinase 1), overcomes LSMs anti-HIV effect. Overall, our studies concluded that LSM is a promising LPA to inhibit HIV-1 infection in myeloid cells in the RIOK1-dependent manner.

microbiology↗

bioRxiv2026

Inhibition of KDM5A/B promotes antitumor innate immune responses in HHV-8/KSHV2 positive B-cell lymphomas

Summary/AbstractHistone methylation is a dynamic and reversible epigenetic modification that critically controls the progression of human diseases, including infections and cancers. Here we reported that histone lysine demethylases (KDMs) in the KDM5 family KDM5A/B play profound roles in suppressing lytic reactivation of oncogenic human herpesvirus 8 (HHV-8), i.e., Kaposis sarcoma-associated herpesvirus (KSHV), as well as antiviral/antitumor innate immune responses in KSHV-infected B-cell lymphomas. We showed that KSHV lytic replication decreases KDM5A/B protein stability by enhancing their K-48 linked polyubiquitination while KDM5A/B depletion facilitates KSHV lytic reactivation. Mechanistic studies illustrated that KDM5A/B associate with KSHV LANA protein and dampen its chromatin association at both KSHV viral lytic promoter and promoters of antitumor immune-responsive genes (IRGs). In comparisons to normal B cells, KDM5A/B expression significantly increased in B-cell lymphoma cells, including KSHV-positive primary effusion lymphoma (PEL). We demonstrated that KDM5A/B inhibition remarkably induces both KSHV lytic reactivation and innate immune responses in PEL cells, resulting in a strong viral oncolytic effect, both in vitro in cell cultures and in vivo using a PEL xenograft mouse model. Overall, our studies identified the novel functions of KDM5A/B to silence KSHV lytic replication and antiviral/antitumor innate immune responses, which can be blocked to benefit the treatment of KSHV-associated B-cell lymphomas that are usually aggressive and difficult to treat.

microbiology↗

bioRxiv2025

NAT10 Suppresses RNA Sensing Induced IFN-β Transactivation to Promote Viral Infection via Interfering with IRF3 Activities

Cells can sense invading viruses and trigger type I interferons (IFN-/{beta}) to evoke antiviral innate immune response. Induction of IFNs needs to be fine-tuned to achieve the antiviral consequence while avoiding severe disruption of host cell homeostasis. Here, we reported that NAT10, the acetyltransferase of histone and N4-acetylcytidine (ac4C) RNA modification, promotes infection of RNA viruses via regulation of type I IFN signaling. Depletion of NAT10 increased the expression of IFN-{beta} and interferon-stimulated genes (ISGs) upon stimulation of type I IFN antiviral signaling, while it impaired viral replication. NAT10 dynamically associated with the IFN-{beta} promotor and negatively regulated IRF3 through modulation of long non-coding RNAs (lncRNAs) that inhibit IRFs. Consistently, the small molecule inhibitor of NAT10, Remodelin, increased IFN-{beta} expression while inhibiting viral infections. Overall, our findings indicated that NAT10 is a negative regulator of type I IFN signaling, suggesting its potential as a target of antiviral treatment.

microbiology↗

bioRxiv2025

m5C RNA Methylation Is Dysregulated by Oncogenic Herpesviruses via c-Myc Signaling to Counteract Host Antiviral Factors

Herpesviruses are a group of double-stranded DNA viruses known to develop versatile viral strategies to escape host immune surveillance for promoting their replication and propagation. This is illustrated by Kaposis sarcoma-associated herpesvirus (KSHV), an oncogenic gamma-herpesvirus that overcomes host immune suppression by multiple mechanisms. In this study, we reported that KSHV dysregulates 5-methylcytosine (m5C) modification and mRNA stability of host antiviral factors to benefit its lytic replication. KSHV lytic reactivation or de novo challenge led to downregulation of m5C RNA methyltransferases, NSUN2 and NSUN1 (NSUN2/1), while NSUN2/1 depletion promoted KSHV lytic replication. Such KSHV-mediated downregulation of NSUN2/1 is via suppression of the transcriptional factor c-Myc. We further performed the RNA bisulfite sequencing (RNA-BS-seq) to identify KSHV-dependent m5C modification of host mRNAs. KSHV lytic reactivation led to the significant reduction of m5C methylation and mRNA stability of TRIM25, a key activator of the RIG-I pathway, while TRIM25 depletion indeed promoted KSHV lytic replication. These host-virus interaction events were also observed in the infection of another oncogenic gamma-herpesvirus Epstein-Barr virus (EBV). Overall, our results highlighted a new strategy for human gamma-herpesviruses to counteract host antiviral factors and promote their lytic replication by manipulating host m5C RNA methylation. Significance StatementOur study has identified a novel viral mechanism of human gamma-herpesviruses to manipulate host RNA methylation machineries to subvert immune defenses and enhance viral lytic replication. In particular, our new data showed that KSHV/EBV downregulate the key 5-methylcytosine (m5C) RNA writers NSUN2/1 via c-Myc, and thus decrease m5C modification and stability of TRIM25 mRNA. As TRIM25 is a key E3 ubiquitin ligase in RIG-I signal transduction, its inhibition disrupts RIG-I mediated antiviral sensing and thus favors viral lytic replication. As human gamma-herpesviruses are critical pathogens that highly associate with multiple human diseases especially certain tumors, such studies are significant to shed light in improving the fundamental understanding of virus-host interactions and identifying new host targets for future translational applications.

microbiology↗

bioRxiv2025

Analysis of Head and Neck Cancer scRNA-seq Data Identified PRDM6 Promotes Tumor Progression by Modulating Immune Gene Expression

Head and neck squamous cell carcinoma (HNSCC) is a biologically aggressive and heterogeneous group of cancers with limited treatment options for patients who do not respond to standard therapies. While HPV-related HNSCCs tend to show better therapeutic outcomes, we still had limited understanding of the immune mechanisms underlying these cancers. Immune-responsive genes (IRGs) have emerged as critical factors in regulating both tumor progression and immune response. Recent advances in single-cell RNA sequencing (scRNA-seq) and the development of cell-type specific regulon inference tools, such as IRIS3, have provided new insights into the tumor immune microenvironment. In this study, we leveraged the IRIS3 platform to analyze scRNA-seq data from HNSCC patient samples, identifying novel transcription factor (TF)-IRG networks that contribute to tumor proliferation and immune escape. Specifically, we identified PRDM6, a histone methyltransferase, possesses the previously unknown role in promoting tumor cell proliferation by inducing IRG expression. We further demonstrated that HPV viral oncoproteins (E6/E7) oncoproteins up-regulate the PRDM6 expression, which associates PRDM6 with HPV-positive HNSCC.

cancer biology↗